Comparison between two-dimensional and three-dimensional dynamic stall

Numerical computations using the DLR-TAU code investigate the differences and similarities between dynamic stall on the two-dimensional OA209 airfoil and the three-dimensional OA209 finite wing. The mean angle of attack in the two-dimensional computations is reduced to match the effective angle of attack at the spanwise position where in the finite wing computations the dynamic stall vortex starts to evolve. Small variations of the mean angle of attack in the two-dimensional numerical simulations show a change from trailing edge separation only to deep dynamic stall. The analysis of the three-dimensional flow field reveals that after the evolution of the dynamic stall vortex the flow field is split into two parts: 1. High spanwise velocity towards the wing’s root in the region between the plane of the first occurrence of stall and the wing’s root. 2. High spanwise velocities towards the wing’s tip in the region between the plane of the first occurrence of stall and wing tip